In different environments there is always an accumulation of particles of various sizes. By monitoring the concentration of particles within a narrow size range, the presence of a fire, even in its earliest stages, within the monitored space may be detected.
There are a number of fire detection devices that are used in both the home and industry that rely upon the accumulation of micron-size particles that can be sensed either by a photo optical or neutron detection device. In more sophisticated devices used in industry, air sampling actually takes place on a continuous basis wherein samples of air from the area being measured are compared with uncontaminated air to obtain a measure of the contamination of the zone. Such a device is shown in the Troup et al. Pat. No. 4,543,815. In other devices, corona-type ionizers are used to charge airborne particulate matter so that these particles can be detected electrically to sense the concentration of the particles. Such a device is described in U.S. Pat. No. 4,312,180.